1. Field of the Invention
The present invention relates to an apparatus for use in a carbon dioxide-capture system, particularly to an apparatus having a basking mechanism allowing micro-algae to photosynthesize and consume carbon dioxide.
2. Description of the Prior Arts
Increased levels of carbon dioxide in the atmosphere have been shown to cause global warming by researchers. Techniques for fixing, absorbing and converting carbon dioxide are believed to be resolutions for global warming and have international significance.
Conventional methods for separating and capturing carbon dioxide include: chemical absorption, physical absorption, physical adsorption, membrane separation and cryogenic separation. The separated or captured carbon dioxide requires subsequent processes, such as chemical conversion, biological conversion or the like to avoid being returned to the environment.
Besides the aforesaid techniques, other techniques utilize photosynthetic ability of micro algae to separate and capture carbon dioxide. Therefore, carbon dioxide can be used as a resource for artificial culture of micro algae. However, atmospheric CO2 limits growth and concentration of micro-algae so increased concentration of CO2 is required, but stirring is not economically viable under low concentrations. Moreover, an amount of micro algae obtained by artificial culture cannot satisfy industrial application. Therefore, additional organic carbon sources need to be added into the culture to enhance the amount of micro algae obtained, resulting in increased continuous costs of culture.
Accordingly, current techniques are developed to include increasing concentration of carbon dioxide in micro alga cultures to enhance growth rate of micro algae. Some techniques utilize increasing stirring rate to culture medium to enhance the accessibility of algae to carbon dioxide in air. However, such stirring requires energy so raises costs and itself causes carbon emissions. Furthermore, for certain strains of micro algae, stirring the micro alga culture at a high rate during culturing causes abnormality of growth and hinders normal physical development of the micro algae.
Other techniques include directly introducing carbon dioxide into the micro alga culture, resulting in increase of uptake of carbon dioxide by micro algae. However, amount of increase is limited and studies show micro algae can only significantly increase uptake of carbon dioxide during conventional artificial culture under increased pressure. A temporary exposure to a high concentration of carbon dioxide under an increased pressure followed by culture under normal condition can facilitate growth of micro algae. However, to establish a high-pressure environment raises costs and consumes energy, contrary to aims of using photosynthetic micro algae to reduce energy use and carbon dioxide emissions.
Other techniques provide a design for use in a hermetic device to capture processed gaseous exhaust containing carbon dioxide. Costs of either construction or operation of the aforesaid design is too high to be economic. Furthermore, oxygen produced by algae from photosynthesis are dissolved in culture of algae under such a hermetic environment, resulting in negative growth conditions for algae.
To overcome the shortcomings, the present invention provides an apparatus and a method for carbon-dioxide capture to mitigate or obviate the aforementioned problems.